Meet Our Home: Planet Earth

Explore a tactile version of our home, the Earth, with household materials.

Lina Canas, Núcleo Interativo de Astronomia

Goals

To explore our home, the Earth, through a tactile hands-on experience for visually impaired students and their non-visually impaired peers.

Learning Objectives

Students will be able to recognise and describe features of the Earth using the tactile model.

Students will be able to explain the importance of building models, identify strengths and limitations of this model, and suggest ways they might improve aspects of the model.

Evaluation

Use the below descriptions or ask students to volunteer their own description for a feature on Earth. Ask students to point at the feature on their diagram as soon as they know which one it is. First give a description and a couple of seconds to think about it. Then give the name and a couple more seconds to point it out. Encourage students to ask questions about different characteristics of Earth represented by the different textures.
e.g.

The part of the world where nearly all humans live. (Land).

These cover nearly three quarters of the Earth’s surface and are very wet. (Seas and oceans).

These are very cold parts of the world, made of ice. (Polar caps).

These are in the sky and where rain comes from. (Clouds).

These are huge storms where the wind is really strong (Hurricane).

Ask students to discuss the importance of building models, strengths and limitations of this model of the Earth, and how they might improve the model.

Ask students in their groups to write down two things they learned from the activity, and two things they want to learn more about.

Materials

Thin wire (for hurricane feature)

Cotton (for clouds and hurricane)

Aluminium foil (for polar caps)

Thick fabric (for continents)

Plastic (for liquid water)

Glue

Scissors

Pen

Earth Features PDF print out

Earth Mold PDF (two copies) print out

Background Information

Earth

Earth is our home and the third planet from the Sun, with a mean distance of about 150 million kilometres. This distance is such that the average surface temperature is above the freezing point of water (0°C) and liquid water can exist freely. This has played a fundamental role in the development of life on our planet, unlike on Venus and Mars, whose surface temperatures are either much warmer or much colder.
The shape of the Earth is very close to a sphere. Because of its slow rotation — once every 24 h — the distortions are small, the difference between the equatorial radius (6,378 km) and the polar radius (6,357 km) being only 21 km. Earth only has one natural satellite, the Moon, which is thought to have played a major role in stabilising the axis of rotation of the Earth. Once again, this may have been a favourable element in the emergence of life.

Tactile features

(while you explore the tactile schematic image)

Liquid water, continents and polar caps

On Earth, 71% of the surface is covered by liquid water (represented by plastic on the tactile image), so the area occupied by seas and oceans is more than twice that occupied by land. The distribution of lands and seas is unequal and peculiar: majority of land masses are in located in the Northern hemisphere as three major continents: Europe, Asia, and North America (continents are represented by the thick fabric on the tactile image). The poles of the Earth are also quite different: there is an ice-covered continent at the South Pole (Antarctica), but an ocean at the North Pole (the Arctic Ocean), which forms an ice cap in winter (both represented by the aluminium foil on the tactile image).
On Earth, surface elevations are measured with respect to the mean sea level. They vary between a height of 8,848 m (Mount Everest) and a depth of 11,000 m (the Mariana Trench in the northwest part of the Pacific Ocean). The average depth of the oceans is 3,800 m, and the average altitude of land is 840 m.

Clouds and hurricanes

Earth has a relatively thin atmosphere extending to less than 200 km altitude. Dry air is mainly composed of nitrogen (N2: 78.08%), oxygen (O2: 20.95%), and argon (Ar: 0.93%). The remaining 0.04% is a mixture of “trace” gases, mostly carbon dioxide (CO2), but also rare gases such as neon (Ne), helium (He), and krypton (Kr). On average, water vapour (H2O) accounts for 0.25% of the mass of the atmosphere, but its concentration varies a lot depending on the local temperature: it can be anywhere between 0.01% and 5%. When lifted to the upper parts of the atmosphere (above 3000 m on average), water vapour condenses to form clouds of very diverse densities and shapes (represented by clumps of cotton on the tactile image); some of these clouds can develop into powerful hurricanes over the oceans (represented by curled wire and cotton on the tactile image).
Earth’s climate has recently begun undergoing an unprecedentedly fast warming phase due to the action of “greenhouse gases”, such as carbon dioxide and methane, that humans have been releasing in large quantities since the beginning of the industrial era. These gases tend to trap infrared radiation from the Earth's surface, causing the Earth's surface to heat up; we call this phenomenon the "greenhouse effect."

Full Activity Description

Prior to the activity:

Print both Earth mold and Earth features PDFs for each group, and prepare the materials listed above.

Ask students what they know about the Earth, and how it looks from space. Tell students they will be making models of the Earth to investigate its different features.

During the activity:

Put the students in groups of 5 (ideally 3 non-visually impaired to 2 visually impaired).

Distribute materials accordingly.

Close supervision is important. Follow each group and explain each of the tactile elements and their correspondence to each object feature.

Understand the different needs of each group of students to promote interaction between the students during the building of the tactile image – visually impaired students need to be familiarized with the different materials involved.

Give enough time to follow instructions and build the tactile image.

Step 1

Print two copies of the 'Earth Mold PDF.'

Step 2

Cut the outer round shape of the Earth from one of the printed papers.

Step 3

Place the paper cutout on top of the plastic and draw the outline.

Step 4

Cut the plastic according to the drawn section.

Step 5

Apply glue on the surface of the Earth in the other printed paper.

Step 6

Place the circular plastic cutout on top of the glued area.

Step 7

Cut the shape of the polar caps on the previously cut 'Earth Mold PDF.'

Step 8

Place the polar caps on aluminium foil and draw the outline.

Step 9

Cut the aluminium foil accordingly to the outline.

Step 10

Glue the aluminium foil (polar caps) on top of the previously glued plastic circular on the paper.

Step 11

Print the 'Earth Features PDF' and cut the shapes of Earth’s continents.

Step 3

Place the paper cutout (continents) on top of the thick fabric and draw the outline.

Step 4

Cut the thick fabric according to the drawn section.

Step 4

Apply glue on the cutout and paste it accordingly on the paper.

Step 14

Curl the cotton around the thin wire to produce the hurricane feature.

Step 15

Curl both textures alike in the size of the round shape of the hurricane.

Step 16

Apply glue and paste it accordingly on the paper.

Step 18

Apply glue on the region denoted by a curved lines.

Step 19

Place cotton on top of the glue to produce the clouds feature.

Wait for the image to dry. This may take a while.

Exploring the tactile image:

There are several ways in which you can explore the scientific content of the tactile schematic images.

If you’re presenting the final tactile image to the students, first let them explore and feel the different textures. Questions will arise as the students explore; encourage them to write their questions down and share with the other groups. Read “Background Information” to understand the different features present in Earth’s schematic tactile image, and share with the students as they ask about them, or (if you have more time), prompt each group to choose a feature to learn more about and then have them present to the other groups in the class.

Water is represented by the plastic texture.

The continents are represented by the thick fabric.

The polar caps by aluminium foil.

The hurricanes are represented by cotton and wire curled up.

The clouds are represented by cotton.

Discuss the idea of models with the students. Suggested discussion points:

What is a model? Why is it useful to build models?

What are the strengths of this model?

What are limitations?

How could the model be improved?

Ask students in their groups to write down two things they learned from the activity, and two things they want to learn more about.